It is well known in the medical arts that the treatment of certain physical conditions benefits markedly by the application of pressure to a body extremity such as an arm or a leg in a manner to promote the flow of a body fluid within the same from a distal portion thereof toward a proximal portion thereof. For example, the afflication known as lymphedema often may cause a limb of the afflicted to swell to a size much greater than normal size as lymphatic fluid accumulates in the limb. One prior mode of treatment for this afflication has been a double-walled sheath or stocking in which air pressure is introduced between the walls to squeeze the limb. It has been found that this and other similar systems which rely on uniform pressure application throughout the length of the afflicated limb do not perform very well and in fact may interfere with the desired distal-to-proximal flow of lymphatic fluid.
Other appoaches to treatment of such disorders have included employment of a sheath that is separated into a number of longitudinally spaced inflatable air cells encircling the limb to be treated. These cells are inflated with uniform air pressure successively from the distal end to the proximal end of the sheath with the intent of promoting fluid flow in the desired direction. However, many of these systems also have been ineffectual as they rely on the air pressure being maintained at the same level or magnitude in all of the pressurized cells. U.S. Pat. Nos. 2,533,504 and 2,781,041 disclose examples of such systems.
Prior U.S. Pat. No. 4,370,975 of one of the joint inventors herein discloses an apparatus for treating lymphedema and similar fluid retention afflications through the use of a multi-cell inflatable sheath which encompasses the swollen limb. Pressure is applied in the cells of the sheath in timed sequence from the distal cell to the proximal cell, the sequence of pressures applied also defining a decreasing gradient pressure from a maximum pressure applied in the distal cell to a minimum pressure applied in the proximal cell when all of the cells are pressurized. Generally, for each of the adjacent cells the more distal has applied therein a higher pressure than the more proximal. This application of gradient pressure from distal to proximal cells in timed sequence, as described, comprises a cycle, and such cycle may be repeated indefinitely to effectively promote the flow of lymphatic fluid from the afflicted limb in a proximal direction.
Prior to introduction of the advance disclosed by the cited prior U.S. Pat. No. 4,370,975 the art did not contemplate any need or desirability for a cell-to-cell pressure gradient in an inflatable appliance of the sort above described.